Field of the Invention
The present invention relates to modified isoprene synthases, polynucleotides which encode such an isoprene synthase, and methods of producing isoprene with such an isoprene synthase.
Discussion of the Background
Natural rubbers are very important raw materials in the tire industry and rubber industries. While demands for rubbers will expand in motorization mainly in developing countries in future, increase of farm plantations is not easy due to regulation to deforestation and competition with palms. Thus, it is predicted that the increase of natural rubber yields is difficult to be anticipated and the balance of demands and supplies will become tight. Synthesized polyisoprene is available as a material in place of the natural rubber, and its raw material monomer, isoprene (2-methyl-1,3-butadiene), is obtained by extracting from a C5 fraction obtained by cracking of naphtha. However in recent years, with lightening in the field of crackers, the production amount of isoprene has tended to decrease, and its supply has been apprehended. Also in recent years, due to strong influence of variation in oil prices, establishment of a system for inexpensively producing isoprene derived from non-oil resource has been required for stably securing an isoprene monomer.
For such a demand, methods of producing the isoprene monomer using a transformant obtained by integrating an isolated isoprene synthase gene derived from kudzu or poplar and its mutant into a bacterium for fermentation production, and the like have been disclosed (see Japanese Laid-Open Publication No. 2011-505841, Japanese Laid-Open Publication No. 2011-518564, US Patent Application Publication No. 2011/0076743, US Patent Application Publication No. 2013/0045891, US Patent Application Publication No. 2013/0295632, US Patent Application Publication No. 2013/0330709, US Patent Application Publication No. 2013/0330796, US Patent Application Publication No. 2013/0295632, US Patent Application Publication No. 2011/0045563, US Patent Application Publication No. 2011/0039323, International Publication WO 2013/016591, Kesselmeier J. et al., Journal of Atmospheric Chemistry, vol. 33, pages 23-88, 1999, Monson R. K. et al., Plant Physiol., vol. 98, pages 1175-1180, 1992, and Kuzma J. et al., Plant Physiol., vol. 101, pages 435-440, 1993, all of which are incorporated herein by reference in their entireties).
There remains, however, a need for improved transformants.